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Apical adenosine regulates basolateral Ca2+-activated potassium channels in human airway Calu-3 epithelial cells

Apical adenosine regulates basolateral Ca2+-activated potassium channels in human airway Calu-3... In airway epithelial cells, apical adenosine regulates transepithelial anion secretion by activation of apical cystic fibrosis transmembrane conductance regulator (CFTR) via adenosine receptors and cAMP/PKA signaling. However, the potent stimulation of anion secretion by adenosine is not correlated with its modest intracellular cAMP elevation, and these uncorrelated efficacies have led to the speculation that additional signaling pathways may be involved. Here, we showed that mucosal adenosine-induced anion secretion, measured by short-circuit current ( I sc ), was inhibited by the PLC-specific inhibitor U-73122 in the human airway submucosal cell line Calu-3. In addition, the I sc was suppressed by BAPTA-AM (a Ca 2+ chelator) and 2-aminoethoxydiphenyl borate (2-APB; an inositol 1,4,5-trisphosphate receptor blocker), but not by PKC inhibitors, suggesting the involvement of PKC-independent PLC/Ca 2+ signaling. Ussing chamber and patch-clamp studies indicated that the adenosine-induced PLC/Ca 2+ signaling stimulated basolateral Ca 2+ -activated potassium (K Ca ) channels predominantly via A 2B adenosine receptors and contributed substantially to the anion secretion. Thus, our data suggest that apical adenosine activates contralateral K + channels via PLC/Ca 2+ and thereby increases the driving force for transepithelial anion secretion, synergizing with its modulation of ipsilateral CFTR via cAMP/PKA. Furthermore, the dual activation of CFTR and K Ca channels by apical adenosine resulted in a mixed secretion of chloride and bicarbonate, which may alter the anion composition in the secretion induced by secretagogues that elicit extracellular ATP/adenosine release. Our findings provide novel mechanistic insights into the regulation of anion section by adenosine, a key player in the airway surface liquid homeostasis and mucociliary clearance. phospholipase C; cystic fibrosis transmembrane conductance regulator; anion secretion; mucociliary clearance Address for reprint requests and other correspondence: P. Huang, Dept. of Biology, Hong Kong Univ. of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, People's Republic of China (e-mail: bohuangp@ust.hk ) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png AJP - Cell Physiology The American Physiological Society

Apical adenosine regulates basolateral Ca2+-activated potassium channels in human airway Calu-3 epithelial cells

Wang, Dong; Sun, Ying; Zhang, Wei; Huang, Pingbo
AJP - Cell Physiology , Volume 294 (6): C1443 – Jun 1, 2008
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References (51)

Publisher
The American Physiological Society
Copyright
Copyright © 2010 the American Physiological Society
ISSN
0363-6143
eISSN
1522-1563
DOI
10.1152/ajpcell.00556.2007
pmid
18385283
Publisher site
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Abstract

In airway epithelial cells, apical adenosine regulates transepithelial anion secretion by activation of apical cystic fibrosis transmembrane conductance regulator (CFTR) via adenosine receptors and cAMP/PKA signaling. However, the potent stimulation of anion secretion by adenosine is not correlated with its modest intracellular cAMP elevation, and these uncorrelated efficacies have led to the speculation that additional signaling pathways may be involved. Here, we showed that mucosal adenosine-induced anion secretion, measured by short-circuit current ( I sc ), was inhibited by the PLC-specific inhibitor U-73122 in the human airway submucosal cell line Calu-3. In addition, the I sc was suppressed by BAPTA-AM (a Ca 2+ chelator) and 2-aminoethoxydiphenyl borate (2-APB; an inositol 1,4,5-trisphosphate receptor blocker), but not by PKC inhibitors, suggesting the involvement of PKC-independent PLC/Ca 2+ signaling. Ussing chamber and patch-clamp studies indicated that the adenosine-induced PLC/Ca 2+ signaling stimulated basolateral Ca 2+ -activated potassium (K Ca ) channels predominantly via A 2B adenosine receptors and contributed substantially to the anion secretion. Thus, our data suggest that apical adenosine activates contralateral K + channels via PLC/Ca 2+ and thereby increases the driving force for transepithelial anion secretion, synergizing with its modulation of ipsilateral CFTR via cAMP/PKA. Furthermore, the dual activation of CFTR and K Ca channels by apical adenosine resulted in a mixed secretion of chloride and bicarbonate, which may alter the anion composition in the secretion induced by secretagogues that elicit extracellular ATP/adenosine release. Our findings provide novel mechanistic insights into the regulation of anion section by adenosine, a key player in the airway surface liquid homeostasis and mucociliary clearance. phospholipase C; cystic fibrosis transmembrane conductance regulator; anion secretion; mucociliary clearance Address for reprint requests and other correspondence: P. Huang, Dept. of Biology, Hong Kong Univ. of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, People's Republic of China (e-mail: bohuangp@ust.hk )

Journal

AJP - Cell Physiology – The American Physiological Society

Published: Jun 1, 2008

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